A multimode wireless communication device is a device that combines at least two different communication access technologies (CATs). The CATs may operate at different frequencies and may operate using different wireless standards, even though the CATs operate within the same frequency band. For example, a multimode handset may support cdma2000 and GSM at 800 MHz, and in a particular market having an A side operator and a B side operator there may be a combination of cdma2000 and GSM. Wireless handsets that support multiple CATs, e.g. CDMA2000, WCDMA, GSM, and WiFi, must determine the appropriate CAT to acquire the available CAT.
If a particular CAT is not available, then the multimode wireless communication device attempts to acquire a different CAT based on a pre-defined search list. The pre-defined search list may be a matrix or a look-up table. Even when a system is found in use, the CAT used in the system may not be the most desirable system due to the type of application launched by the user or the cost of the service due to roaming agreements. Thus, it is common for the multimode wireless communication device to continue with searches for alternate CATs.
Although the procedure for searching is straightforward, depending on the user's location and system availability, the amount of power used for searching for alternative CATs may be excessive. Furthermore, searching for an alternative CAT often requires the multimode wireless communication device to tune away from the current CAT disrupting ongoing services if the multimode wireless communication device is not capable of simultaneous CAT operation. Even if the multimode wireless device supports simultaneous operation on two CATs, the process of searching for an alternative CAT requires that the corresponding receiver module be turned on to process the CAT or determine the availability of the CAT.
Current multimode wireless communication devices have dedicated CAT receiver circuitry that meets the requirements set forth by standard performance requirements. In some cases, the wireless operator may add even more stringent requirements than those specified in the standard. Thus each CAT receiver module, in the multimode wireless communication device actively attempting to receive signals from the corresponding CAT network, is a drain on system resources such as the battery.
Acquisition time is also important. For wireless devices capable of simultaneous operation, it is possible that each CAT receiver be actively attempting to acquire networks for faster acquisition time. For wireless multimode devices not capable of simultaneous operation, the order for searching CAT may have a dramatic impact on acquisition time.
With respect to Software Defined Radio (SDR), although the receiver chain may be shared among multiple CATs, the SDR is bound by the standard performance requirements where a lower limit is set on the power consumption to perform a search. Thus, again each CAT must be actively attempting to receive signals from corresponding CAT network resulting in a drain of system resources.